Composite materials are used in a wide variety of applications, particularly in the automotive sector. Such applications include, for example, vehicle body panels as well as vehicle frame components. Newer wheel constructions include composite materials being used as center elements attached to aluminum rims.
The composite material used in such applications is made by combining two or more individual materials in both continuous and discontinuous forms to maximize their useful properties and to minimize their weaknesses. The material in the continuous form is called matrix while the material in the discontinuous form is embedded (or dispersed) in the matrix. The embedded material is usually stronger than the surrounding matrix material, and thus is sometimes called reinforcing material.
Reinforcing materials are usually in the form of plates, fibers or particles that have random or preferred orientation within the matrix. The matrix binds the reinforcing materials together somewhat like an adhesive, thereby making them more resistant to external damage. The reinforcing materials make the matrix stronger and stiffer and help it to resist cracks and fractures. The reinforcing materials are typically glass, carbon, silicon carbide, or asbestos, while the matrix is usually a polymer, metal, or ceramic material.
The primary advantages of known composite materials are their net high strength, relatively low weight, and high degree of corrosion resistance. These advantages provide the main reasons for the increasing use of composite materials for industrial applications in which the component from a composite material has no or somewhat limited exposure to dynamic loading such as shocks, impacts or repeated cyclic loading.
Dynamic loading can cause composites to fail on both the microscopic or macroscopic scale. Macroscopic scale failures can be net section failures of the part due to material fatigue resulting from the cyclic variation of the induced stress. A microscopic scale failure can occur when one or more of the layers in the composite fail in tension of the matrix or in the bond between the matrix and fibers or at each individual reinforcing fiber in compression buckling. This can occur due to either material fatigue resulting from the cyclic variation of the induced stress or due to high instantaneous stress caused by the impact or shock loading. The poor performance of the known composite materials under dynamic loading is mainly attributed to their relatively low internal damping, i.e., their inability to quickly convert vibrational or impact energy to heat or sound.
To aid in predicting and preventing failures, composites are extensively tested before and after construction, which appears to have discouraged their widespread use. The expanded use of composite materials is further restricted according to known technology as composites are generally known to have relatively poor bearing strength when compared to metals.
In view of the state of the art, it may be advantageous to provide composite components with appropriate cast-in components that aid in damping. As in so many areas of manufacturing technology, there is always room for improvement in damping by adding friction damping to interacting mechanical and structural components.